In the chemical industry, many processes conducted in a plant include the step of treating effluent or exhaust gases from a process machine. The treatment is necessary to either complete a chemical reaction such that unreacted chemicals are not released into the atmosphere, or to convert toxic or flammable components of an exhaust gas into non-toxic or non-flammable components before they are released into the atmosphere. The treatment of effluent gases is particularly important in a semiconductor fabrication plant since most of the process gases utilized are either highly toxic or highly flammable.
A controlled decomposition/oxidation (or CDO) system 10 that is equipped with recirculation and sump pumps is shown as an example in FIG. 1. One of such CDO system is marketed by the Delatech Corp. of Napa, Calif. as part of an exhaust gas conditioning equipment. The system 10 is effective in treating or scrubbing exhaust gases through a thermal reaction section 12 and a cooling/scrubbing section 14. Exhaust gases 18 from a semiconductor process chamber enter into the system through inlet 20 and are first treated in an oxygenation reaction section 22. The oxygenated exhaust gases then enter the thermal reaction section 12 which is heated by heating elements 24. Heating elements 24 are powered by an electric wiring fed through a wiring connector (not shown) and controlled by thermocouple 28.
The thermally reacted exhaust gases then enter into a primary cooling/scrubbing section 30 which is equipped with a conduit cleaning apparatus 34 and a cleaning water supply line 36. Cooling water (not shown) is sprayed through a plurality of nozzles 38 to cool off the high temperature thermally reacted exhaust gases. The temperature of the thermally reacted exhaust gases can reach above 800.degree. C. and therefore must be cooled before it is processed by the secondary cooling/scrubbing section 14. The cleaning apparatus 34 is constructed of a gear 42 that has two cleaning blades 46 installed thereon for scrapping an interior wall 26 to remove unwanted chemical substances deposited thereon. A detailed description of the cleaning apparatus 34 will be given in a later section in reference to FIG. 2.
The function of the cleaning apparatus 34 is to remove the chemical substances (not shown) that have been cumulated and deposited on the interior wall 26 of the exhaust conduit 54 in the thermal reaction section 12. These chemical substances include a variety of high temperature films, nitride powders and films, etc., which normally form a hard and highly resilient substance that is difficult to remove.
Cooled exhaust gases enter into the secondary cooling/scrubbing section 14 and are treated by the scrub packing 48 before it is released to the atmosphere through an outlet 52. The apparatus 10 is effective for treating exhaust gases from a semiconductor fabrication machine that contains toxic elements by first treating in a high temperature oxygenation reaction, converting to a lower temperature, and then converting toxic substances into non-toxic substances such that they can be safely released into the atmosphere.
In the exhaust gas reactor shown in FIG. 1, it has been found that while the apparatus generally achieves the desirable results of toxic gas conversions, a deposition of hard chemical substances on the interior wall 26 in the thermal reaction section 12 can not be avoided. A conventional conduit cleaning apparatus 34 which is equipped with scrapping blades 46 and water spray nozzles 38 is not effective in cleaning the exhaust conduit 54. A detailed perspective view of the components in the cleaning apparatus 34 is shown in FIG. 2.
FIG. 2 is a perspective view of the components of the cleaning apparatus 34. The components include an upper support bracket 56, a pair of cleaning blades 58, a flange plate 60, a Teflon bearing 62, a gear wheel 64, a flange housing 66, a solenoid operated drive 68 which has a push rod 70 installed thereon, a lower Teflon bearing 62 and a lower flange plate 72. The key mechanism of the cleaning apparatus 34 is the cleaning blades 58, the gear wheel 64 and the solenoid driven cylinder 68 together with the push rod 70. In operation, unidirectional gear teeth 74 located on the face of the gear wheel 64 are pushed by the push rod 70 each time the solenoid driven cylinder 68 is activated. The cleaning blades 58 are each equipped with a single knife edge (not shown) such that they perform an unidirectional cleaning operation of the interior wall 26 (FIG. 1) of the thermal reaction section 12. Each time the tip 76 of the push rod 70 advances the gear wheel 64 by 1/16 of the circumference of the interior wall 26. In general, it takes about 160 seconds for the cleaning blades to make a complete sweep of the circumferential surface of the interior wall 26.
Numerous problems have been observed in utilizing the conduit cleaning apparatus 34 during an exhaust gas treatment process. For instance, the displacement of the cleaning blades 58 is limited such that they do not clean the interior wall efficiently. Secondly, since there are only two blades and only one knife edge available for unidirectional cleaning, the cleaning efficiency of the two blades is limited. Thirdly, the high load on the cleaning blades frequently causes the blade to deform and thus stops its cleaning function. Fourthly, the mounting screws of the cleaning blades to the gear wheel 64 frequently break or otherwise deform to disable the blades. Various other problems may also be caused by a disfunctioning of the push rod mounted on the solenoid driven cylinder 68. For instance, the tip 76 of the push rod may break or deform such that the gear teeth 74 on the gear wheel 64 are not touched and as a result, the advancement of the cleaning blades 58 completely stops. Furthermore, the push rod 70 frequently jam between the flange housing and the gear wheel 64 to cause the cleaning apparatus to stop functioning.
In a copending application, Ser. No. 09/141,065, filed Aug. 27, 1998, assigned to the common assignee of the present invention and incorporated here by reference in its entirety, an apparatus for cleaning a conduit and a method for using the apparatus are disclosed.
It is therefore an object of the present invention to provide an apparatus for cleaning a conduit that has unwanted substances coated on an interior wall that does not have the drawbacks and shortcomings of a conventional cleaning apparatus.
It is another object of the present invention to provide an apparatus for cleaning a conduit that has unwanted substances deposited on an interior wall by utilizing a rack-and-pinion drive mechanism for driving at least three cleaning blades.
It is a further object of the present invention to provide an apparatus for cleaning a conduit that has unwanted substances deposited on an interior wall by utilizing cleaning blades that are equipped with two oppositely facing knife blades such that the blades may clean in both a clockwise and a counterclockwise directions.
It is another further object of the present invention to provide an apparatus for cleaning a cavity in an exhaust gas reactor by utilizing a pinion gear equipped with at least three cleaning blades installed thereon and driven by a rack such that a linear motion of the rack is transformed into a rotational motion of the pinion gear allowing the cleaning blades to scrape the interior wall of the cavity.
It is still another object of the present invention to provide an apparatus for cleaning a cavity in an exhaust gas reactor by utilizing three upper cleaning blades and three lower cleaning blades which are securely mounted inside bores in a pinion gear that is at least 3 cm thick such that not only the cavity in the exhaust gas reactor but also a chamber below such cavity of the reactor can be cleaned.
It is yet another object of the present invention to provide an apparatus for cleaning a cavity in an exhaust gas reactor wherein at least three cleaning blades are mounted on a pinion gear such that knife edges on the cleaning blades are situated in a circumference that is not more than 10 mm smaller than a circumference of an interior wall of the cavity.
It is still another further object of the present invention to provide a method for cleaning a conduit that has unwanted substances coated on an interior wall of the conduit by utilizing a cleaning apparatus that comprises a tall pinion gear and at least three cleaning blades installed therein for scrapping the interior wall of the conduit.
It is yet another further object of the present invention to provide a method for cleaning a conduit that has unwanted substances coated on an interior wall of the conduit by first providing a cleaning apparatus that includes a tall pinion gear with at least three cleaning blades securely mounted therein each having two oppositely facing knife blades such that the cleaning blades cleans in both directions when the pinion gear turns in a clockwise or in a counterclockwise direction.